The present invention relates to a light beam hardening apparatus.
Light beam hardening apparatus for dental material hardening applications are today configured either as hand-held devices for the direct light polymerization of the dental material in the mouth of the dental patient or as stationary devices.
In particular with regard to hand-held devices, it is important that the polymerization be effected relatively rapidly and, at the least, at a rate which ensures a complete polymerization as well of larger teeth fillings comprised of light beam hardenable plastic.
The conventional light beam hardening apparatus is by far typically configured as a halogen bulb lamp having integrated reflectors whose light emissions are guided by a light guide rod, with the outlet end of the light guide rod being disposed immediately adjacent the filling to be hardened. The typical light beam hardenable dental plastic exhibits a spectral sensitivity whose maximum sensitivity lies in the region of visible light.
On the other hand, typical commercially available halogen bulb lamps emit visible light with substantially reduced ultraviolet (UV) portions of about 2%, for example. To improve the efficiency of the emitted light impact, it has been attempted to extend the spectral sensitivity of the plastic material which is to be polymerized into the long wavelength region. These attempts, however, have only succeeded in limited measure.
It has been further proposed to extend the emitted spectral region into the higher frequencies by means of filters, which only permit the passage therethrough of high wavelength light. This approach, however, requires that a substantial amount of light emitting energy be initially produced whereby, as a consequence thereof, the efficiency of this approach is correspondingly poor. At the same time, a cooling air flow must be regularly introduced which acts to limit the temperature of the light beam hardening apparatus and this air flow is not altogether pleasant for the dentist or the dental patient.
Moreover, it has long been known to deploy as light beam hardening apparatus semi-conductor light emitting sources which operate as light emitting diodes (LED). For example, German patent publication DE-GM 295 11 927 discloses a light beam hardening apparatus having a light emitting diode which emits light in the blue spectral region and which is powered by a battery or an accumulator.
It has been additionally proposed to deploy a plurality of LEDs for the power supply of a light guide rod. In this manner, the light output of the light beam hardening apparatus is improved. However, independent of whether the LEDs are configured and emit light as modulesxe2x80x94that is, deployed in a common plastic housingxe2x80x94or as individual LEDsxe2x80x94that is, each deployed in its own respective plastic housing, the light output of LEDs is limited. The plastic housings are not only electrically insulating but they also suppress the shedding of heat so that a certain performance thickness of each of the light emitting chips cannot be exceeded due to the need to provide cooling of the plastic housings from the exterior.
It has, moreover, been proposed in other applications to adhesively secure light emitting chips on a metallic body. The heat resistance between the chip and the cooling body in such a configuration is, in fact, less than that of a configuration in which a chip is integrated into a plastic module. However, the adhesive layer acts as a heat blocker so that the danger exists here as well of an overheating of the chip or chips.
It has also long been a practice in the mounting of semi-conductors on cooling bodies to use a heat conducting paste. The heat conducting paste should displace a continuously insulating air layer which, due to the surface roughness of the outer surface, acts as a barrier to heat shedding. In spite of all efforts, however, the known light beam hardening apparatus with semi-conductor light emitting sources produce only a limited light output and are in this respect not especially suitable for dental applications.
The present invention offers a solution to the challenge of providing a light beam hardening apparatus which shortens the light hardening time so that a particularly strong heating up inside the mouth of the patient does not also occur due to the dental material hardening procedure.
In accordance with the present invention, it is particularly advantageous that, for the most part, cold light is used. A relatively reduced light strength is generated such that the long wavelength emission component is suppressed, whereby the intensity of the light beam radiation is higher in comparison to that of conventional devices.
The light beam hardening apparatus of the present invention unexpectedly generates a reduced temperature level in the mouth of the dental patient. As a first explanation for this, the intensive emissions shorten the handling time so that only a reduced heating up occurs in the area of the filling. However, a further explanation for this phenomenon lies in the fact that the temperature range of the light beam hardening apparatus is itself surprisingly markedly lower so that there is no particularly intensive heating from this source.
The heat from the light emissions from the chip are, in accordance with the present invention, immediately conducted away via heat conducting connections to a base receptacle of substantial size. This base receptacle is itself then heated up. However, the base receptacle can be very effectively cooled in that it can be configured with a substantially large outer surface. The base receptacle has, however, due to its mass, a particularly large heat capacity so that its temperature is raised by only a relatively modest amount in the event of a premature disposition of heat energy in the course of just a few seconds.
In an advantageous embodiment of the light beam hardening apparatus of the present invention, a so-called heat pipe is provided for conducting heat rearwardly away from the base receptacle. The thus rearwardly conducted heat can be in effect given off to the environment so that this embodiment can even be operated in a manner which does not require the blowing of cooling air onto the light beam hardening apparatus.
In another advantageous embodiment of the light beam hardening apparatus of the present invention, it is provided that each chip in the cradle is recessed relative to the outer surface of the cradle. This configuration results in a still further improved light emission efficiency. The cradle is preferably provided with an interior mirrored or reflective surface and operates as a micro reflector whereby the outer surfaces of the light emitting chips can be disposed in the focal burning point of the micro reflector. By virtue of this configuration, the light emitted toward the side is focused so that the loss of light caused by misdirected light emissions is markedly reduced.
In accordance with a further advantageous embodiment of the light beam hardening apparatus of the present invention, micro reflectors having integrated chips of the configuration just described are uniformly distributed over the outer surface of the base receptacle. The light emissions produced from this arrangement are bundled together in the front directionxe2x80x94that is, are emitted toward the location to be hardened by the light emissionsxe2x80x94whereby the individual light emission bundles overlap and mix together.
In connection with such light emission bundling, it is also possible to provide various colors of the emission spectra of the individual chips and to undertake an individual control of each chip""s emissions. For example, a focused red light can be emitted if, in a modified embodiment of the light beam hardening apparatus of the present invention, a heat handling procedure is to be performed.
It is particularly favorable, in one embodiment of the light beam hardening apparatus of the present invention, to use double connector wires. The especially light intensive chips of the light beam hardening apparatus of the present invention have high requirements for power, and the use of two gold or aluminum wires, each 30 xcexcm, between the power supply conduit and the chip has shown itself as adequate for handling the power supply needs of the chips.
In another advantageous embodiment of the light beam hardening apparatus of the present invention, which is particularly suited for high performance chips, the so-called flip-chip technology can be implemented. In this connection, the contact is made to the underside of the chip and light emission is from the topside of the chip. The use of a bonded wire connection can be dispensed with in this embodiment as the contact can be accomplished, for example, by soldering.
In accordance with the present invention, the metallic heat conducting connection can be manufactured in any desired, suitable manner. For example, the base receptacle can also be manufactured with two coats and, in fact, with a metallic over coat and a ceramic base coat. Also, in accordance with the present invention, a substantially large heat capacity can be built in, especially if the metallic over coat completely covers the ceramic base coat and/or the silicon body, whereby the heat distribution is in this respect improved. Alternatively, an aluminum body can be used.
In a further advantageous embodiment of the light beam hardening apparatus of the present invention, it is provided that the base receptacle is generally configured in cup form and, in fact, is configured in a form which corresponds precisely to that of the receptacle or socket which has previously been used to support a halogen bulb lamp with reflectors. The receptacle or socket has cooling ribs along its outer surface and the base receptacle is preferably connected to the receptacle via heat conducting paste. An exchange during the life of the light beam hardening apparatus is as a rule generally not required as the LED chips have a very long operational life so that cost savings relative to light beam hardening apparatus with halogen bulb lamps are achieved due to reduced maintenance costs. It is particularly advantageous that the light beam hardening apparatus of the present invention eliminates the risk which is present in connection with halogen bulb lamps, that the breaking off of the polymerization procedure is caused by a burning through of the bulb lamp, thus resulting in a half hardened filling which must then be removed.
In a particularly advantageous embodiment of the light beam hardening apparatus of the present invention, it is provided that the emitted light beams are intensified onto a surface of limited cross sectional area by a prism body. The prism body is configured such that it shifts the individual light beam emissions in the outer region of the base receptacle emissions into the middle so that they can be guided practically without loss of light into the light guide rod. The prism body can additionally be enclosed within a cooling body having longitudinal cooling ribs on its exterior which facilitate the shedding of heat.
It is particularly advantageous, in one embodiment of the light beam hardening apparatus of the present invention, if the base receptacle including individual LED chips is substituted for a halogen bulb lamp having reflectors in a hand-held light hardening device. In this configuration, the exterior of the base receptacle is dimensioned so as to correspond with the dimensions of the inner surface of the receptacle, which receives the halogen bulb lamp. It is preferable if the exterior of the base receptacle is configured as a truncated cup and that connection pins are provided at those same locations as such connection pins are provided on halogen bulb lamps. The substitution of an appropriately dimensioned base receptacle of the light beam hardening apparatus of the present invention for a 50 W halogen bulb lamp offers a significantly improved emitted light performance for the same electrical power input. If the light beam hardening apparatus is controlled by a programmable controller, then, in the event that the base receptacle of the light beam hardening apparatus of the present invention has been substituted for a halogen bulb lamp with reflectors, the material hardening time will be correspondingly shortened to, for example, one-half the customary hardening time or even one-third the customary hardening time, which is a time saving benefit for the dentist.